Block-signal system.



UNITED STATES PATENT OI FIQE.

ELMER F. BLISS, OF SCHENECTADY, NEW YORK, ASSIGNOR TO GENERAL ELECTRICCOM- PANY, A CORPORATION OF NEW YORK.

BLOCK-SIGNAL SYSTEIVI.

Specification of Letters Patent.

Patented July 23, 1907;

Application filed March 7, 1906. Serial No. 304,649.

To all whom it may concern:

Be it known that I, .ELMER F. BLIss, a citizen of the United States,residing at Schenectady, county of Schenectady, State of New York,haveinvented certain new anduseful Improvements in Block-Signal Systems, ofwhich the following is a specification.

My invention relates to block signal systems, and its object is toprovide simple and efiicient means for protecting the source of currentconnected to the track circuit from an abnormal flow of current whenshortcircuited by a train. I

It has been proposed heretofore to protect the source by means of aresistance inserted when the current rises above a predetermined amount.

My invention consists in cutting a portion of the source out of circuitupon an abnormal flow of current. By means of this arrangement theprotective resistance may be greatly reduced in amount, or even omittedentirely, so that the loss of power is reduced and the efiiciency of thesystem increased.

While my invention in its broadest aspect is not limited to a signalsystem employing any particular form of current, it is particularlyadvantageous for use in alternating-current signal systems in which thetrack circuits are supplied from transformers. In a directcurrent signalsystem in which the track circuits are supplied from batteries theinternal resistance of the battery is ordinarily high enough to preventa flow of current large enough to injure the battery when shortcircuitedbya train on the block, but when a transformer is the source of supply,the internal resistance is small.

I shall,'accordingly, describe my invention as applied to an alternatingsignal system, but it will be understood that it is equally applicableto a direct-current signal system, if it is desired to protect thedirect-current source against an abnormal flow.

My invention will best be understood by reference to the accompanyingdrawing, which shows diagrammatically a block signal system providedwith protective devices arranged in accordance with my invention.

In the drawing R, R, represent the track-rails of a road which, in thepresent case, is assumed to be an electrically operated road, the supplyconductors for the power-current being indicated at T.

A, A, represent line-wires carrying alternating-current at high tension,which is supplied to the track circuit through the step-downtransformers B, B.

C, C, represent transformers having their primaries supplied from thestep-down transformers B, B, and

their secondaries connected to the track circuit.

7 D, D, represent transformers connected to the other ends of theblocks,their secondaries supplying a coil of the relays E, E. I

In order to provide a return path for thepower-current the central pointof the secondaries of each transformer C is connected to the centralpoint of the primary of transformer D at the adjacent end of theadjacent block. The adjacent blocks are thus connected at equipotentialpoints with respect to the signal current, and this connection enablesthe rails to serve as conductors for both the signal-current andpower-current without mutual interference, as is fully described inlatents Nos; 645,907 and 647,741, issued to Badell, dated March 20,1900, and April 17, l900,respectively. The relays E are shown as of thepolyphase induction type, one primary coil being supplied from the tracktransformer D and the other directly or through a transformer from thealternating-current supply conductors A. When both phases of the relayare energized, as is the case when no train is on the track, the contactmember carried by the armature of the relay closes a circuit comprisingthe signal operating mechanism F of the signal H and asuitable source ofcurrent G. The signaloperating mechanism is merely indicateddiagrammatically, as it forms no part of the present invention, and anywell-known type of operating mechanism may be employed. I representsarelay in series with the secondary of the transformer B and the primaryof transformer C. J represents an impedance, preferably a non-inductiveresistance.

The operation is as follows: Normally the relaysI are in the positionshown, in which the full voltage of the secondaries of transformers Bare supplied to the pri maries of transformers C. When a train on ablock short-circuits the secondary of a transformer C, thereby producingan abnormal flow of current, the correspondingrelay I draws up itsarmature, cutting out a portion of the secondary oi transformer B andincluding in circuit the impedance J. In this manner, the voltagesupplied to the track circuit is reduced and the flow of excessivecurrent due to the short-circuiting effect of the train is prevented.Since the impedance .T is normally out of circuit, it does not impairthe eiliciency of the system.

I do not desire to limit myself to the particular construction andarrangement of parts here shown, but aim in the appended claims to coverall modifications which are within the scope of my invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is,-

1. In a block signal system, in combination with the rail circuit of ablock, a source of voltage supplying the rail circuit, and an overloadrelay in series with said source arranged to cut a portion of saidsource out of circuit upon an abnormal flow of current therefrom.

In a block signal system, in combination with the rail circuit of :1block, a source of voltage supplying the rail circuit, an overload relayin series with said source arranged to cut :1 portion of said source outof circuit upon ,an abnormal fl0w of-current therefrom, and an impedancearranged to be inserted in series with said source by the gredncingthenumber of effective secondary turns of said transformers upon anabnormal flow of current therein. 4. In an alternating-current blocksignal system, linewires extending along the track, supply connectionsfrom the line-wires to the rail circuits of the blocks, transformerscomprised in'said'connections, and overload relays in said connectionscomprising contacts arran ed to cut a portion ot the secondarj turns ofsaid transformers out of circuit.

5. In an alter-nating-current block signal system, linewires extendingalong the track, supply connections from the line-wires to the railcircuits of the block, transformers comprised in said connections, andmeans for increasing the ratio of effective primary to eifectivesecondary turns in said transformers upon abnormal flow'of currenttherein.

In witness whereof, I have hereunto set my hand this 6th day of March,1906.

' ELMER F. BLISS.

Witnesses:

BENJAMIN B. HULL, HnLnN ORFoRD.

